Disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the velocity of the actuator arm as it seeks from track to track.
When manufacturing a disk drive, a number of tests are typically performed in order to calibrate various parameters associated with accessing each disk surface. For example, a bias setting may be calibrated for each head that enables the read element to read data from a corresponding disk surface. Other parameters that may be calibrated include read channel parameters, such as equalizer settings, gain settings, sequence detector settings, etc. that enable accurate demodulation of the read signal generated by each head. If a head is determined to be defective (read or write element), the head is typically disabled and the corresponding head/disk pair not used in the disk drive.